Wakeup-free ferroelectric memory device

ABSTRACT

The present disclosure relates to a method for forming a ferroelectric memory device. The method includes forming a dielectric layer over a semiconductor substrate and forming a first conductive layer over the dielectric layer. The first conductive layer has a first overall electronegativity. A ferroelectric layer is formed on the first conductive layer. The ferroelectric layer has a second overall electronegativity less than or equal to the first overall electronegativity. A second conductive layer is formed on the ferroelectric layer. The second conductive layer has a third overall electronegativity greater than or equal to the second overall electronegativity. The second conductive layer, the ferroelectric layer, and the first conductive layer are etched to form a polarization switching structure. An ILD layer is formed over the polarization switching structure, and a planarization process is performed on the ILD layer. A first conductive via is formed over the polarization switching structure.

REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of U.S. application Ser. No. 17/117,711, filed on Dec. 10, 2020, which is a Divisional of U.S. application Ser. No. 16/405,058, filed on May 7, 2019 (now U.S. Pat. No. 10,879,391, issued on Dec. 29, 2020). The contents of the above-referenced Patent Applications are hereby incorporated by reference in their entirety.

BACKGROUND

Many modern day electronic devices include non-volatile memory. Non-volatile memory is electronic memory that is able to store data in the absence of power. A promising candidate for the next generation of non-volatile memory is ferroelectric random-access memory (FeRAM). FeRAM has a relatively simple structure and is compatible with complementary metal-oxide-semiconductor (CMOS) logic fabrication processes.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 illustrates a cross-sectional view of some embodiments of a first integrated chip (IC) comprising a first wakeup-free ferroelectric memory device.

FIG. 2 illustrates a magnified cross-sectional view of some embodiments of the device gate stack of FIG. 1 .

FIG. 3 illustrates a top view of some embodiments of the first conductive structure, the ferroelectric structure, and the second conductive structure removed from their stacked orientation in FIG. 1 and disposed next to one another.

FIG. 4 illustrates a cross-sectional view of some more detailed embodiments of the first IC of FIG. 1 .

FIG. 5 illustrates a cross-sectional view of some other embodiments of the first IC of FIG. 4 .

FIG. 6 illustrates a cross-sectional view of some other embodiments of the first IC of FIG. 4 .

FIG. 7 illustrates a cross-sectional view of some embodiments of a second IC comprising a second wakeup-free ferroelectric memory device.

FIG. 8 illustrates a cross-sectional view of some other embodiments of the second IC of FIG. 7 .

FIG. 9 illustrates a cross-sectional view of some other embodiments of the second IC of FIG. 7 .

FIG. 10 illustrates a cross-sectional view of some other embodiments of the second IC of FIG. 9 .

FIGS. 11-20 illustrate a series of cross-sectional views of some embodiments for forming the first IC of FIG. 5 .

FIG. 21 illustrates a flowchart of some embodiments of a method for forming an IC comprising a front-end-of-line wakeup-free ferroelectric memory device.

FIG. 22 illustrates a flowchart of some embodiments of a method for forming an IC comprising a back-end-of-line wakeup-free ferroelectric memory device.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

Some ferroelectric memory (e.g., ferroelectric random-access memory (FeRAM)) comprises a ferroelectric memory cell. The ferroelectric memory cell comprises a ferroelectric structure disposed between a first electrode and a second electrode. In other embodiments, the ferroelectric structure may be disposed between a gate electrode and a semiconductor substrate (e.g., ferroelectric field-effect transistor (FeFET). The ferroelectric structure is configured to switch between polarization states to store data (e.g., binary “0” and “1”). The ferroelectric memory is often disposed on an integrated chip (IC) comprising other types of semiconductor devices (e.g., metal-oxide semiconductor field-effect transistors (MOSFETs), bipolar junction transistors (BJTs), high-electron-mobility transistors (HEMTs), etc.).

A challenge with the above ferroelectric memory is a need to perform a wakeup procedure on the ferroelectric memory cell to improve the memory window of the ferroelectric memory cell. For example, after the ferroelectric memory cell has been off (e.g., disconnected from power) for a given time period, the memory window of the ferroelectric memory cell may degrade to an unsatisfactory condition. Therefore, each time the ferroelectric memory cell is turned on, the wakeup procedure needs to be performed to improve the memory window of the ferroelectric memory cell, such that the ferroelectric memory cell may function properly (e.g., read, write, erase). The wakeup procedure comprises providing a plurality of voltage pulses, which may consist of different voltage amplitudes and pulse widths, to the ferroelectric memory cell.

In order to perform the wakeup procedure, wakeup circuitry is disposed on the IC to provide the voltage pulses to the ferroelectric memory cell. The wakeup procedure may negatively affect performance of the ferroelectric memory due to the wakeup procedure increasing power consumption of ferroelectric memory. Further, the wakeup circuitry takes up space on the IC that may be utilized to increase the density/number of ferroelectric memory cells.

In some embodiments, the present disclosure relates to a wakeup-free ferroelectric memory device. The wakeup-free ferroelectric memory device comprises a polarization switching structure. The polarization switching structure comprises a ferroelectric structure disposed between a first conductive structure and a second conductive structure. Both the first conductive structure and the second conductive structure have an overall electronegativity that is greater than or equal to an overall electronegativity of the ferroelectric structure. Because the overall electronegativity of both the first conductive structure and the second conductive structure are greater than the overall electronegativity of the ferroelectric structure, a wakeup procedure is not required to improve a memory window of the wakeup-free ferroelectric memory device. For example, because the overall electronegativity of both the first conductive structure and the second conductive structure are greater than the overall electronegativity of the ferroelectric structure, the memory window of the wakeup-free ferroelectric memory device may not degrade to an unsatisfactory condition after power has been removed from the polarization switching structure. In other words, the wakeup-free ferroelectric memory device does not require a wakeup procedure to improve the memory window of the wakeup-free ferroelectric memory device to function properly (e.g., read, write, erase). Accordingly, compared to non-wakeup-free ferroelectric memory, the wakeup-free ferroelectric memory may consume less power and/or have a greater number (or density) of ferroelectric memory devices on a given IC.

FIG. 1 illustrates a cross-sectional view of some embodiments of a first integrated chip (IC) 100 comprising a first wakeup-free ferroelectric memory device 101 a. In some embodiments, the first wakeup-free ferroelectric memory device 101 a illustrated in FIG. 1 may be referred to as a wakeup-free ferroelectric field-effect transistor (FeFET) and/or a front-end-of-line wakeup-free ferroelectric memory device. In further embodiments, the first wakeup-free ferroelectric memory device 101 a may be part of a random-access memory (RAM) device (e.g., ferroelectric random-access memory (FeRAM) device). It will be appreciated that, in some embodiments, the first wakeup-free ferroelectric memory device 101 a of FIG. 1 could be realized in a fin type design (e.g., FinFET type design). It will further be appreciated that, in some embodiments, the first IC 100 may comprise a plurality of first wakeup-free ferroelectric memory devices 101 a disposed in an array.

As shown in FIG. 1 , the first IC 100 comprises an isolation structure 104 disposed in a semiconductor substrate 102. A pair of source/drain regions 106 a-b are disposed in the semiconductor substrate 102 and spaced apart. A device gate stack 120 is disposed over the semiconductor substrate 102 and between the source/drain regions 106 a-b. In some embodiments, the first wakeup-free ferroelectric memory device 101 a comprises the device gate stack 120 and the source/drain regions 106 a-b. An interlayer dielectric (ILD) structure 122 is disposed over the semiconductor substrate 102 and the device gate stack 120. A plurality of conductive contacts 124 are disposed in the ILD structure 122. The conductive contacts 124 extend through the ILD structure 122 to contact the source/drain regions 106 a-b and the device gate stack 120, respectively.

In some embodiments, the device gate stack 120 comprises a gate dielectric 108 disposed on the semiconductor substrate 102. A polarization switching structure 110 is disposed between the gate dielectric 108 and a gate electrode 118. The polarization switching structure 110 is configured to store a bit of data. For example, the polarization switching structure 110 may switch between a first polarization state (e.g., negative remnant (−Pr) polarization state), which corresponds to a binary value of “1,” and a second polarization state (e.g., positive remnant (+Pr) polarization state), which corresponds to a binary value of “0,” or vice versa. In some embodiments, a positive voltage pulse is applied to the gate electrode 118 to switch to the first polarization state, and a negative voltage pulse is applied to the gate electrode 118 to switch to the second polarization state, or vice versa.

The polarization switching structure 110 comprises a ferroelectric structure 114 disposed between a first conductive structure 112 and a second conductive structure 116. The first conductive structure 112 has an overall electronegativity that is greater than or equal to an overall electronegativity of the ferroelectric structure 114. The second conductive structure 116 has an overall electronegativity that is greater than or equal to the overall electronegativity of the ferroelectric structure 114. More specifically, both the overall electronegativity of the first conductive structure 112 and the overall electronegativity of the second conductive structure 116 are greater than or equal to the overall electronegativity of the ferroelectric structure 114.

“Overall electronegativity” (X_(compound (or element))) is based on the chemical composition of a compound (or element), percent of atoms of the chemical composition, and the electronegativity of the element(s) by the Pauling scale. An equation to determine the overall electronegativity of a generic compound (A_(x)B_(y) . . . N_(z)) is provided below:

$X_{A_{x}B_{y}\ldots N_{z}} = {{X_{rA}\frac{x}{x + y + {\cdots z}}} + {X_{rB}\frac{x}{x + y + {\cdots z}}} + {\cdots X_{rN}\frac{z}{x + y + {\cdots z}}}}$

where X_(AxBy . . . Nz) is the overall electronegativity of compound A_(x)B_(y) . . . N_(z), A is a first element, B is a second element, N is an Nth element, X_(rA) is the electronegativity of the first element by the Pauling scale, X_(rB) is the electronegativity of the second element by the Pauling scale, X_(rN) is the electronegativity of the Nth element by the Pauling scale, x is the number atoms of the first element in compound A_(x)B_(y) . . . N_(z), y is the number of atoms of the second element in compound A_(x)B_(y) . . . N_(z), and z is the number of atoms of the first element in compound A_(x)B_(y) . . . N_(z).

Some non-limiting examples are provided below illustrating the calculation of “overall electronegativity” for a variety of elements/compounds.

EXAMPLE 1 Overall Electronegativity of Tungsten (X_(W))

Electronegativity of W by Pauling scale (X_(rW))—2.36

$X_{W} = {X_{rW}\frac{1}{1}}$ X_(W) = 2.36

EXAMPLE 2 Overall Electronegativity of Hafnium Oxide (X_(HfO) ₂ )

Electronegativity of Hf by Pauling scale (X_(rHf))—1.3

Electronegativity of O by Pauling scale (X_(rO))—3.44

$X_{{Hf}O_{2}} = {{H_{rHf}\frac{1}{1 + 2}} + {X_{rO}\frac{2}{1 + 2}}}$ $X_{{Hf}O_{2}} = {{1.3\left( \frac{1}{3} \right)} + {3.44\left( \frac{2}{3} \right)}}$ X_(HfO₂) = 2.72

EXAMPLE 3 Overall Electronegativity of Hafnium-Zirconium-Oxide (X_(HfZrO) ₄ )

Electronegativity of Hf by Pauling scale (X_(rHf))—1.3

Electronegativity of Zr by Pauling Scale (X_(rZr))—1.33

Electronegativity of O by Pauling scale (X_(rO))—3.44

$X_{{HfO}_{2}} = {{X_{rHf}\frac{1}{1 + 1 + 4}} + {X_{rZr}\frac{1}{1 + 1 + 4}} + {X_{rO}\frac{4}{1 + 1 + 4}}}$ $X_{{HfZrO}_{2}} = {{1.3\left( \frac{1}{6} \right)} + {{1.3}3\left( \frac{1}{6} \right)} + {{3.4}4\left( \frac{4}{6} \right)}}$ X_(HfZrO₂) = 2.73

Because the overall electronegativity of the first conductive structure 112 and the overall electronegativity of the second conductive structure 116 are greater than or equal to the overall electronegativity of the ferroelectric structure 114, a memory window of the first wakeup-free ferroelectric memory device 101 a may not degrade to an unsatisfactory condition after power has been removed from the polarization switching structure 110. In other words, the first wakeup-free ferroelectric memory device 101 a does not require a wakeup procedure to improve the memory window of the first wakeup-free ferroelectric memory device 101 a to function properly (e.g., read, write, erase). Accordingly, compared to non-wakeup-free ferroelectric memory, the first wakeup-free ferroelectric memory device 101 a may consume less power and/or the first IC 100 may comprise a greater number (or have a greater density) of the first wakeup-free ferroelectric memory devices 101 a.

FIG. 2 illustrates a magnified cross-sectional view of some embodiments of the device gate stack 120 of FIG. 1 .

The gate electrode 118 may comprise, for example, doped polysilicon (e.g., n-type/p-type polysilicon), a metal (e.g., tungsten (W), aluminum (Al), titanium (Ti), molybdenum (Mo), nickel silicide (NiSi), or the like), some other conductive material, or a combination of the foregoing. In some embodiments, a capping structure (not shown) (e.g., titanium nitride (TiN), tantalum nitride (TaN), or the like) may be disposed between the gate electrode 118 and the second conductive structure 116. In further embodiments, the gate electrode 118 and/or the capping structure has an overall electronegativity that is less than the overall electronegativity of the ferroelectric structure 114. In yet further embodiments, when the gate electrode 118 comprises a metal, the gate electrode 118 (and the capping structure) may be referred to as a metal gate electrode.

In some embodiments, the gate dielectric 108 may comprise, for example, an oxide (e.g., silicon dioxide (SiO₂)), a high-k dielectric material (e.g., hafnium oxide (HfO₂), zirconium oxide (ZrO₂), or some other dielectric material with a dielectric constant greater than about 3.9), some other dielectric material, or a combination of the foregoing. In further embodiments, an overall electronegativity of the gate dielectric 108 is less than the overall electronegativity of the ferroelectric structure 114.

In some embodiments, the first conductive structure 112 may comprise, for example, a metal (e.g., aluminum (Al), titanium (Ti), tantalum (Ta), gold (Au), platinum (Pt), tungsten (W), nickel (Ni), iridium (Ir), etc.), a metal-nitride (e.g., titanium nitride (TiN), tantalum nitride (TaN), etc.), a metal-oxide (e.g., iridium oxide (IrO₂)), doped polysilicon (e.g., n-type/p-type polysilicon), or the like. In further embodiments, the ferroelectric structure 114 may comprise one or more layers of, for example, a metal-oxide (e.g., hafnium oxide (Hf_(X)O_(Y))), a component-metal-oxide (e.g., hafnium-silicon-oxide (Hf_(X)Si_(Y)O_(Z)), hafnium-aluminum-oxide (Hf_(X)Al_(Y)O_(Z)), hafnium-gadolinium-oxide (Hf_(X)Gd_(Y)O_(Z)), hafnium-zirconium-oxide (Hf_(X)Zr_(Y)O_(Z)), hafnium-lanthanum-oxide (Hf_(X)La_(Y)O_(Z)), hafnium-strontium-oxide (Hf_(X)Sr_(Y)O_(Z)), hafnium-yttrium-oxide (Hf_(X)Y_(Y)O_(Z)), strontium titanate (STO), etc.), a metal-oxynitride (e.g., hafnium oxynitride (Hf_(X)O_(Y)N_(Z))), or the like. In yet further embodiments, the second conductive structure 116 may comprise, for example, a metal (e.g., Al, Ti, Ta, Au, Pt, W, Ni, Ir, etc.), a metal-nitride (e.g., TiN, TaN, etc.), a metal-oxide (e.g., IrO₂), doped polysilicon (e.g., n-type/p-type polysilicon), or the like.

The first conductive structure 112 and the second conductive structure 116 may have a same chemical composition. In other embodiments, the chemical composition of the first conductive structure 112 may be different than the chemical composition of the second conductive structure 116. The overall electronegativity of the first conductive structure 112 may be greater than the overall electronegativity of the gate dielectric 108. In further embodiments, the overall electronegativity of the second conductive structure 116 may be greater than the overall electronegativity of the gate electrode 118 (or the capping structure).

In some embodiments, the first conductive structure 112 contacts both the gate dielectric 108 and the ferroelectric structure 114, the second conductive structure 116 contacts both the ferroelectric structure 114 and the gate electrode 118, and the gate electrode 118 contacts one of the conductive contacts 124. In further embodiments, sidewalls of the gate dielectric 108, sidewalls of the first conductive structure 112, sidewalls of the ferroelectric structure 114, sidewalls of the second conductive structure 116, and sidewalls of the gate electrode 118 may be substantially aligned in a vertical direction. In such embodiments, an area (e.g. length (across the page of FIG. 2 ) times width (into/out of the page of FIG. 2 )) of the gate dielectric 108, an area of the first conductive structure 112, an area of the ferroelectric structure 114, an area of the second conductive structure 116, and an area of the gate electrode 118 may be substantially the same. In other embodiments, the sidewalls of the first conductive structure 112 may be disposed between the sidewalls of the gate dielectric 108, the sidewalls of the ferroelectric structure 114 may be disposed between the sidewalls of the first conductive structure 112, the sidewalls of the second conductive structure 116 may be disposed between the sidewalls of the ferroelectric structure 114, and/or the sidewalls of the gate electrode 118 may be disposed between the sidewalls of the second conductive structure 116. In such embodiments, the area of the first conductive structure 112 may be less than the area of the gate dielectric 108, the area of the ferroelectric structure 114 may be less than the area of the first conductive structure 112, the area of the second conductive structure 116 may be less than the area of the ferroelectric structure 114, and/or the area of the gate electrode 118 may be less than the area of the second conductive structure 116.

In some embodiments, the area of the gate dielectric 108 may be between about 1 square nanometer (nm²) and about 100 square micrometers (um²). In further embodiments, an area of the polarization switching structure 110 is between about 1 nm² and about 100 um². In yet further embodiments, the area of the gate dielectric 108 may be substantially the same as the area of the polarization switching structure 110. In other embodiments, the area of the gate dielectric 108 may be different than the area of the polarization switching structure 110.

The polarization switching structure 110 has a first thickness T₁. In some embodiments, the first thickness T₁ is between about 1.2 nanometer (nm) and about 2,100 nm. The first conductive structure 112 has a second thickness T₂. The second thickness T₂ may be between about 0.1 nm and about 1,000 nm. The ferroelectric structure 114 has a third thickness T₃. In some embodiments, the third thickness is between about 1 nm and about 100 nm. The second conductive structure 116 has a fourth thickness T₄. The fourth thickness T₄ may be between about 0.1 nm and about 1,000 nm. The gate dielectric 108 has a fifth thickness T₅. In further embodiments, a ratio between the first thickness T₁ and the fifth thickness T₅ (e.g., T₁ divided by T₂) is between about 100/1 and about 1/1.

In some embodiments, the second thickness T₂, the third thickness T₃, and the fourth thickness T₄ are substantially the same. In further embodiments, the second thickness T₂ and the fourth thickness T₄ may be substantially the same, while the third thickness T₃ differs. In further embodiments, the second thickness T₂ (or the fourth thickness T₄) and the third thickness T₃ may be substantially the same, while the fourth thickness T₄ (or the second thickness T₂) differs. In yet further embodiments, the second thickness T₂, the third thickness T₃, and the fourth thickness T₄ may differ from one another.

FIG. 3 illustrates a top view of some embodiments of the first conductive structure 112, the ferroelectric structure 114, and the second conductive structure 116 removed from their stacked orientation in FIG. 1 and disposed next to one another.

As shown in FIG. 3 , the first conductive structure 112 has a first length L₁ and a first width W₁. In some embodiments, the first length L₁ may be between about 1 nm and about 10 micrometers (um). In further embodiments, the first width W₁ may be between about 1 nm and about 10 um. In yet further embodiments, the area (e.g., L₁ times W₁) of the first conductive structure 112 is between about 1 nm² and about 100 um².

The ferroelectric structure 114 has a second length L₂ and a second width W₂. In some embodiments, the second length L₂ may be between about 1 nm and about 10 um. In further embodiments, the second width W₂ may be between about 1 nm and about 10 um. In yet further embodiments, the area (e.g., L₂ times W₂) of the ferroelectric structure 114 is between about 1 nm² and about 100 um².

The second conductive structure 116 has a third length L₃ and a third width W₃. In some embodiments, the third length L₃ may be between about 1 nm and about 10 um. In further embodiments, the third width W₃ may be between about 1 nm and about 10 um. In yet further embodiments, the area (e.g., L₃ times W₃) of the second conductive structure 116 is between about 1 nm² and about 100 um².

FIG. 4 illustrates a cross-sectional view of some more detailed embodiments of the first IC 100 of FIG. 1 .

As shown in FIG. 4 , a plurality of conductive lines 402 (e.g., metal lines) and a plurality of conductive vias 404 (e.g., metal vias) are disposed in the ILD structure 122. The plurality of conductive lines 402, the plurality of conductive vias 404, and the plurality of conductive contacts 124 are electrically coupled together in a predefined manner and configured to provide electrical connections between various devices disposed throughout the first IC 100. In some embodiments, the plurality of conductive lines 402 and the plurality of conductive vias 404 may comprise, for example, copper (Cu), aluminum (Al), or the like. In further embodiments, the conductive contacts 124 may comprise, for example, tungsten (W), copper (Cu), aluminum (Al), or the like. The plurality of conductive lines 402 have a sixth thickness T₆. In further embodiments, a ratio between the sixth thickness T₆ and the first thickness T₁ (e.g., T₆ divided by T₁) is between about 200/1 and about 0.5/1. It will be appreciated that any number of conductive lines 402 and/or conductive vias 404 may be alternately stacked over one another in the ILD structure 122. In yet further embodiments, the plurality of conductive lines 402, the plurality of conductive vias 404, the plurality of conductive contacts 124, and the ILD structure 122 may be referred to as an interconnect structure.

A first one of the plurality of conductive lines 402 is denoted as 402 wl and may be referred to as a word line. In some embodiments, the word line may be electrically coupled to the polarization switching structure 110 via the interconnect structure and the gate electrode 118. A second one of the plurality of conductive lines 402 is denoted as 402 bl and may be referred to as a bit line. In further embodiments, the bit line may be electrically coupled to a first source/drain region 106 a of the source/drain regions 106 a-b via the interconnect structure. A third one of the plurality of conductive lines 402 is denoted as 402 sl and may be referred to as a source line. In yet further embodiments, the source line may be electrically coupled to a second source/drain region 106 b of the source/drain regions 106 a-b via the interconnect structure.

In some embodiments, the semiconductor substrate 102 may comprise any type of semiconductor body (e.g., monocrystalline silicon/CMOS bulk, silicon-germanium (SiGe), silicon on insulator (SOI), etc.). The isolation structure 104 may be, for example, a shallow trench isolation (STI) structure, a deep trench isolation (DTI) structure, or the like. In further embodiments, the source/drain regions 106 a-b are doped regions of the semiconductor substrate 102 that have a doping type (e.g., n-type or p-type) opposite that of adjoining regions of the semiconductor substrate 102, or the adjoining regions of the semiconductor substrate 102 may be intrinsic. The ILD structure 122 may comprise one or more stacked ILD layers, which may respectively comprise a low-k dielectric (e.g., a dielectric material with a dielectric constant less than about 3.9), an oxide (e.g., SiO₂), or the like.

FIG. 5 illustrates a cross-sectional view of some other embodiments of the first IC 100 of FIG. 4 .

As shown in FIG. 5 , the ILD structure 122 comprise a first ILD structure 122 a and a second ILD structure 122 b. The second ILD structure 122 b is disposed over the first ILD structure 122 a and the device gate stack 120. In some embodiments, an upper surface of the first ILD structure 122 a may be substantially co-planar with an upper surface of the gate electrode 118. In further embodiments, the first ILD structure 122 a may comprise one or more stacked ILD layers. In yet further embodiments, the second ILD structure 122 b may comprise one or more stacked ILD layers.

A pair of lightly-doped source/drain extensions (LDDs) 504 a-b are disposed in the semiconductor substrate 102 and spaced apart. The LDDs 504 a-b are doped regions of the semiconductor substrate 102 having a same doping type as the source/drain regions 106 a-b. The LDDs 504 a-b have a lower doping concentration than the source/drain regions 106 a-b. A sidewall spacer 502 is disposed over the semiconductor substrate 102 and along sidewalls of the gate dielectric 108, the polarization switching structure 110, and the gate electrode 118. In further embodiments, the sidewall spacer 502 may comprise, for example, a nitride (e.g., silicon nitride (e.g., SiN)), an oxy-nitride (e.g., silicon oxy-nitride (SiO_(X)N_(Y))), or the like.

FIG. 6 illustrates a cross-sectional view of some other embodiments of the first IC 100 of FIG. 4 .

As shown in FIG. 6 , one of the plurality of conductive contacts 124 contacts the second conductive structure 116. In such embodiments, the device gate stack 120 may not comprise the gate electrode 118 (see, e.g., FIG. 5 ).

FIG. 7 illustrates a cross-sectional view of some embodiments of a second IC 700 comprising a second wakeup-free ferroelectric memory device 101 b. In some embodiments, the second wakeup-free ferroelectric memory device 101 b may be referred to as a back-end-of-line wakeup-free ferroelectric memory device. In further embodiments, the second wakeup-free ferroelectric memory device 101 b may be part of a RAM device (e.g., FeRAM device). It will be appreciated that, in some embodiments, features of the second IC 700 that share a reference numeral with features of the first IC 100 may have substantially similar properties (e.g., dimensions, chemical compositions, relationships, etc.) as the features of the first IC 100 in which they share a reference numeral. It will further be appreciated that, in some embodiments, the second IC 700 may comprise a plurality of the second wakeup-free ferroelectric memory devices 101 b disposed in an array.

As shown in FIG. 7 , a semiconductor device 702 is disposed on the semiconductor substrate 102. In some embodiments, the semiconductor device 702 may be a metal-oxide semiconductor field-effect transistors (MOSFETs), bipolar junction transistors (BJTs), high-electron-mobility transistors (HEMTs), or any other front-end-of-line semiconductor device. In further embodiments, the semiconductor device 702 may comprise a gate dielectric 108, a gate electrode 118 disposed over the gate dielectric 108, and a pair of source/drain regions 106 a-b.

A lower ILD structure 704 is disposed over the semiconductor substrate 102 and the semiconductor device 702. In some embodiments, a plurality of conductive contacts 124, a plurality of conductive lines 402, and a plurality of conductive vias 404 are disposed in the lower ILD structure 704. An upper ILD structure 708 is disposed over the lower ILD structure 704. In further embodiments, a plurality of conductive lines 402 and/or a plurality of conductive vias 404 are disposed in the upper ILD structure 708. A middle ILD structure 706 is disposed between the upper ILD structure 708 and the lower ILD structure 704. In yet further embodiments, the lower ILD structure 704, the middle ILD structure 706, and the upper ILD structure 708 may comprise one or more stacked ILD layers, which may respectively comprise a low-k dielectric (e.g., a dielectric material with a dielectric constant less than about 3.9), an oxide (e.g., SiO₂), or the like.

The second wakeup-free ferroelectric memory device 101 b is disposed in the middle ILD structure 706. The second wakeup-free ferroelectric memory device 101 b comprises a polarization switching structure 110. The polarization switching structure 110 comprises a ferroelectric structure 114 disposed between a first conductive structure 112 and a second conductive structure 116. In some embodiments, an upper surface of the second conductive structure 116 is substantially co-planar with an upper surface of the middle ILD structure 706. In further embodiments, a lower surface of the first conductive structure 112 is substantially co-planar with a lower surface of the middle ILD structure 706.

In some embodiments, the polarization switching structure 110 is electrically coupled to the second source/drain region 106b of the semiconductor device 702 via the plurality of conductive lines 402, the plurality of conductive vias 404, and the plurality of conductive contacts 124 disposed in the lower ILD structure 704. A fourth one of the plurality of conductive lines 402 is denoted as 402 pl and may be referred to as a plate line. In further embodiments, the plate line may be electrically coupled to the polarization switching structure 110 via the plurality of conductive lines 402 and/or conductive vias 404 disposed in the upper ILD structure 708. In yet further embodiments, one of the plurality of conductive vias 404 (or conductive lines 402) disposed in the lower ILD structure 704 may contact the first conductive structure 112, and one of the plurality of conductive vias 404 (or conductive lines 402) disposed in the upper ILD structure 708 may contact the second conductive structure 116.

The first conductive structure 112 has an overall electronegativity that is greater than or equal to an overall electronegativity of the ferroelectric structure 114. The second conductive structure 116 has an overall electronegativity that is greater than or equal the overall electronegativity of the ferroelectric structure 114. More specifically, both the overall electronegativity of the first conductive structure 112 and the overall electronegativity of the second conductive structure 116 are greater than or equal to the overall electronegativity of the ferroelectric structure 114.

Because the overall electronegativity of the first conductive structure 112 and the overall electronegativity of the second conductive structure 116 are greater than or equal to the overall electronegativity of the ferroelectric structure 114, a memory window of the second wakeup-free ferroelectric memory device 101 b may not degrade to an unsatisfactory condition after power has been removed from the polarization switching structure 110. In other words, the second wakeup-free ferroelectric memory device 101 b does not require a wakeup procedure to improve the memory window of the second wakeup-free ferroelectric memory device 101 b to function properly (e.g., read, write, erase). Accordingly, compared to non-wakeup-free ferroelectric memory, the second wakeup-free ferroelectric memory device 101 b may consume less power and/or the second IC 700 may comprise a greater number (or have a greater density) of the second wakeup-free ferroelectric memory devices 101 b.

FIG. 8 illustrates a cross-sectional view of some other embodiments of the second IC 700 of FIG. 7 .

As shown in FIG. 8 , some of the plurality of conductive lines 402, the plurality of conductive vias 404, and the plurality of conductive contacts 124 disposed in the lower ILD structure 704 electrically couple the second wakeup-free ferroelectric memory device 101 b to the gate electrode 118 of the semiconductor device 702.

FIG. 9 illustrates a cross-sectional view of some other embodiments of the second IC 700 of FIG. 7 .

As shown in FIG. 9 , a first electrode 902 and a second electrode 904 are disposed on opposite sides of the polarization switching structure 110. In some embodiments, the first electrode 902 and/or the second electrode 904 are disposed in the middle ILD structure 706. In other embodiments, the first electrode 902 is disposed in the lower ILD structure 704 and/or the second electrode 904 is disposed in the upper ILD structure 708.

The first electrode 902 contacts the first conductive structure 112 and is disposed between the first conductive structure 112 and the semiconductor substrate 102. The second electrode 904 contacts the second conductive structure 116, and the polarization switching structure 110 is disposed between the second electrode 904 and the semiconductor substrate 102. In some embodiments, one of the plurality of conductive vias 404 (or conductive lines 402) disposed in the lower ILD structure 704 may contact the first electrode 902, and one of the plurality of conductive vias 404 (or conductive lines 402) disposed in the upper ILD structure 708 may contact the second electrode 904. In further embodiments, the first electrode 902 may comprise, for example, Al, Ti, Ta, Au, Pt, W, Ni, Ir, TiN, TaN, some other conductive material, or a combination of the foregoing. In yet further embodiments, the second electrode 904 may comprise, for example, Al, Ti, Ta, Au, Pt, W, Ni, Ir, TiN, TaN, some other conductive material, or a combination of the foregoing.

In some embodiments, the first electrode 902 and the second electrode 904 may have a same chemical composition. In other embodiments, the chemical composition of the first electrode 902 may be different than the chemical composition of the second electrode 904. The overall electronegativity of the first conductive structure 112 may be greater than or equal to the overall electronegativity of the first electrode 902. In yet further embodiments, the overall electronegativity of the second conductive structure 116 may be greater than or equal to the overall electronegativity of the second electrode 904.

In some embodiments, sidewalls of first electrode 902, sidewalls of the first conductive structure 112, sidewalls of the ferroelectric structure 114, sidewalls of the second conductive structure 116, and sidewalls of the second electrode 904 may be substantially aligned in a vertical direction. In such embodiments, an area (e.g. length (across the page of FIG. 2 ) times width (into/out of the page of FIG. 2 )) of the first electrode 902, an area of the first conductive structure 112, an area of the ferroelectric structure 114, an area of the second conductive structure 116, and an area of the second electrode 904 may be substantially the same. In other embodiments, the sidewalls of the first conductive structure 112 may be disposed between the sidewalls of the first electrode 902, the sidewalls of the ferroelectric structure 114 may be disposed between the sidewalls of the first conductive structure 112, the sidewalls of the second conductive structure 116 may be disposed between the sidewalls of the ferroelectric structure 114, and/or the sidewalls of the second electrode 904 may be disposed between the sidewalls of the second conductive structure 116. In such embodiments, the area of the first conductive structure 112 may be less than the area of the first electrode 902, the area of the ferroelectric structure may be less than the area of the first conductive structure 112, the area of the second conductive structure 116 may be less than the area of the ferroelectric structure 114, and/or the area of the second electrode 904 may be less than the area of the second conductive structure 116.

FIG. 10 illustrates a cross-sectional view of some other embodiments of the second IC 700 of FIG. 9 .

As shown in FIG. 10 , some of the plurality of conductive lines 402, the plurality of conductive vias 404, and the plurality of conductive contacts 124 disposed in the lower ILD structure 704 electrically couple the second wakeup-free ferroelectric memory device 101 b to the gate electrode 118 of the semiconductor device 702.

FIGS. 11-20 illustrate a series of cross-sectional views of some embodiments for forming the first IC 100 of FIG. 5 .

As shown in FIG. 11 , an isolation structure 104 is formed within a semiconductor substrate 102. In some embodiments, the isolation structure 104 may be formed by selectively etching the semiconductor substrate 102 to form a trench in the semiconductor substrate 102, and subsequently filing the trench with a dielectric material. In further embodiments, the semiconductor substrate 102 is selectively etched by forming a masking layer (not shown) over the semiconductor substrate 102, and subsequently exposing the semiconductor substrate 102 to an etchant configured to selectively remove unmasked portions of the semiconductor substrate 102. In yet further embodiments, the dielectric material may comprise an oxide (e.g., SiO₂), a nitride, a carbide, or the like.

As shown in FIG. 12 , a dielectric layer 1202, a first conductive layer 1204, a ferroelectric layer 1206, a second conductive layer 1208, and a processing layer 1210 are formed over the isolation structure 104 and the semiconductor substrate 102. In some embodiments, the dielectric layer 1202 is formed on the semiconductor substrate 102 and the isolation structure 104. The first conductive layer 1204 may be formed on the dielectric layer 1202. The ferroelectric layer 1206 is formed on the first conductive layer 1204. The second conductive layer 1208 is formed on the ferroelectric layer 1206. The processing layer 1210 may be formed on the second conductive layer 1208.

In some embodiments, a process for forming the dielectric layer 1202 comprises depositing or growing the dielectric layer 1202 on the semiconductor substrate 102. In further embodiments, the dielectric layer 1202 may comprise, for example, an oxide (e.g., SiO₂), a high-k dielectric material (e.g., HfO2, ZrO2, or some other dielectric material with a dielectric constant greater than about 3.9), some other dielectric material, or a combination of the foregoing. In yet further embodiments, the dielectric layer 1202 may be deposited or grown by thermal oxidation, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), sputtering, or some other deposition or growth process.

In some embodiments, a process for forming the first conductive layer 1204 comprises depositing or growing the first conductive layer 1204 on the dielectric layer 1202. In further embodiments, the first conductive layer 1204 may comprise, for example, a metal (e.g., Al, Ti, Ta, Au, Pt, W, Ni, Ir, etc.), a metal-nitride (e.g., TiN, TaN, etc.), a metal-oxide (e.g., IrO₂), doped polysilicon (e.g., n-type/p-type polysilicon), or the like. In yet further embodiments, the first conductive layer 1204 may be deposited or grown by CVD, PVD, ALD, epitaxy, sol-gel, sputtering, electrochemical plating, electroless plating, or some other deposition or growth process.

In some embodiments, a process for forming the ferroelectric layer 1206 comprises depositing or growing the ferroelectric layer 1206 on the first conductive layer 1204. In further embodiments, the ferroelectric layer 1206 may comprise, for example, a metal-oxide (e.g., Hf_(X)O_(Y)), a component-metal-oxide (e.g., Hf_(X)Si_(Y)O_(Z), Hf_(X)Al_(Y)O_(Z), Hf_(X)Gd_(Y)O_(Z), Hf_(X)Zr_(Y)O_(Z), Hf_(X)La_(Y)O_(Z), Hf_(X)Sr_(Y)O_(Z), Hf_(X)Y_(Y)O_(Z), STO, etc.), a metal-oxynitride (e.g., Hf_(X)O_(Y)N_(Z)), or the like. In yet further embodiments, the ferroelectric layer 1206 may be deposited or grown by CVD, PVD, ALD, epitaxy, sol-gel, sputtering, electrochemical plating, electroless plating, or some other deposition or growth process.

In some embodiments, a process for forming the second conductive layer 1208 comprises depositing or growing the second conductive layer 1208 on the ferroelectric layer 1206. In further embodiments, the second conductive layer 1208 may comprise, for example, a metal (e.g., Al, Ti, Ta, Au, Pt, W, Ni, Ir, etc.), a metal-nitride (e.g., TiN, TaN, etc.), a metal-oxide (e.g., IrO₂), doped polysilicon (e.g., n-type/p-type polysilicon), or the like. In yet further embodiments, the second conductive layer 1208 may be deposited or grown by CVD, PVD, ALD, epitaxy, sol-gel, sputtering, electrochemical plating, electroless plating, or some other deposition or growth process.

In some embodiments, a process for forming the processing layer 1210 comprises depositing or growing the processing layer 1210 on the second conductive layer 1208. In further embodiments, the processing layer 1210 may comprise, for example, polysilicon (doped or undoped), an oxide (e.g., SiO₂), or some other material that may be selectively etched in relation to the second conductive layer 1208. In yet further embodiments, the processing layer 1210 may be deposited or grown by CVD, PVD, ALD, epitaxy, sputtering, or some other deposition or growth process.

The first conductive layer 1204 has an overall electronegativity that is greater than or equal to an overall electronegativity of the ferroelectric layer 1206. The second conductive layer 1208 has an overall electronegativity that is greater than or equal to the overall electronegativity of the ferroelectric layer 1206. More specifically, both the overall electronegativity of the first conductive layer 1204 and the overall electronegativity of the second conductive layer 1208 are greater than or equal to the overall electronegativity of the ferroelectric layer 1206.

In some embodiments, the overall electronegativity of the first conductive layer 1204 is greater than or equal to an overall electronegativity of the dielectric layer 1202. The overall electronegativity of the dielectric layer 1202 may be less than the overall electronegativity of the ferroelectric structure 114. The first conductive layer 1204 and the second conductive layer 1208 may have a same chemical composition. In other embodiments, the chemical composition of the first conductive layer 1204 may be different than the chemical composition of the second conductive layer 1208.

In some embodiments, the first conductive layer 1204 is formed as a conformal layer having a thickness between about 0.1 nm and about 1,000 nm. The ferroelectric layer 1206 may be formed as a conformal layer having a thickness between about 1 nm and about 100 nm. In further embodiments, the second conductive layer 1208 is formed as a conformal layer having a thickness between about 0.1 nm and about 1,000 nm. A combined thickness of the first conductive layer 1204, the ferroelectric layer 1206, and the second conductive layer 1208 may be between about 1.2 nm and about 2,100 nm. In yet further embodiments, the dielectric layer 1202 is formed as a conformal layer having a thickness that is between about 1/100 and about 1/1 the combined thickness of the first conductive layer 1204, the ferroelectric layer 1206, and the second conductive layer 1208.

As shown in FIG. 13 , the dielectric layer 1202, the first conductive layer 1204, the ferroelectric layer 1206, the second conductive layer 1208, and the processing layer 1210 (see, e.g., FIG. 12 ) are patterned into an initial gate stack 1302. The initial gate stack 1302 comprises a polarization switching structure 110 disposed between a gate dielectric 108 and a sacrificial gate 1304. The polarization switching structure 110 comprises a ferroelectric structure 114 disposed between a first conductive structure 112 and a second conductive structure 116.

In some embodiments, a process for forming the initial gate stack 1302 comprises forming a patterned masking layer 1306 (e.g., positive/negative photoresist) over/on the processing layer 1210. The patterned masking layer 1306 may be formed by a spin-on process and patterned using photolithography. Thereafter, an etch (e.g., wet/dry etch) is performed into the processing layer 1210, the second conductive layer 1208, the ferroelectric layer 1206, the first conductive layer 1204, and the dielectric layer 1202 with the patterned masking layer 1306 in place. The etch removes unmasked portions of the processing layer 1210, the second conductive layer 1208, the ferroelectric layer 1206, the first conductive layer 1204, and the dielectric layer 1202, thereby forming the sacrificial gate 1304, the second conductive structure 116, the ferroelectric structure 114, the first conductive structure 112, and the gate dielectric 108, respectively. Subsequently, the patterned masking layer 1306 may be stripped away.

In some embodiments, the initial gate stack 1302 may be formed by a single patterning process. In other embodiments, the initial gate stack 1302 may be formed by multiple patterning processes, each of which pattern one (or a combination) of the processing layer 1210, the second conductive layer 1208, the ferroelectric layer 1206, the first conductive layer 1204, and the dielectric layer 1202. It will be appreciated that, in some embodiments, one (or a combination) of the first conductive layer 1204, the ferroelectric layer 1206, the second conductive layer 1208, and the processing layer 1210 may be patterned prior to a layer being subsequently formed thereon. For example, the dielectric layer 1202 may be deposited and then patterned into the gate dielectric 108 before the first conductive layer 1204 is formed on the gate dielectric 108.

As shown in FIG. 14 , a pair of lightly-doped source/drain extensions (LDDs) 504 a-b are formed in the semiconductor substrate 102. The LDDs 504 a-b are formed on opposite sides of the initial gate stack 1302. In some embodiments, the LDDs 504 a-b are formed by an ion implantation process and may utilize a masking layer (not shown) to selectively implant ions in the semiconductor substrate 102. In further embodiments, the initial gate stack 1302 may be utilized as the masking layer to form the LDDs 504 a-b.

As shown in FIG. 15 , a sidewall spacer 502 is formed over the semiconductor substrate 102 and along sides of the initial gate stack 1302. In some embodiments, the sidewall spacer 502 may be formed by depositing a spacer layer (not shown) over the semiconductor substrate 102 and the initial gate stack 1302. In further embodiments, the spacer layer may comprise a nitride (e.g., SiN), an oxy-nitride (e.g., SiO_(X)N_(Y)), or the like. The spacer layer may be deposited by PVD, CVD, ALD, sputtering, or some other deposition process. Subsequently, the spacer layer is etched to remove the spacer layer from horizontal surfaces, leaving the spacer layer along sides of the initial gate stack 1302 as the sidewall spacer 502. In yet further embodiments, the sidewall spacer 502 may be formed prior to forming the LDDs 504 a-b. In such embodiments, the LDDs 504 a-b may be formed using an angled ion implantation process.

As illustrated by FIG. 16 , a pair of source/drain regions 106 a-b are formed in the semiconductor substrate 102. The source/drain regions 106 a-b are formed on opposite sides of the sidewall spacer 502. In some embodiments, the source/drain regions 106 a-b are formed by an ion implantation process and may utilize a masking layer (not shown) to selectively implant ions into the semiconductor substrate 102. In further embodiments, the initial gate stack 1302 and the sidewall spacer 502 may be utilized as the masking layer to form the source/drain regions 106 a-b.

As shown in FIG. 17 , a first interlayer dielectric (ILD) structure 122 a is formed over the semiconductor substrate 102 and the isolation structure 104. The first ILD structure 122 a may be formed with a substantially planar upper surface that is co-planar with an upper surface of the sidewall spacer 502. In some embodiments, a process for forming the first ILD structure 122 a comprises depositing an ILD layer on the semiconductor substrate 102, the isolation structure 104, the sidewall spacer 502, and the sacrificial gate 1304 (see, e.g., FIG. 16 ). The ILD layer may be deposited by CVD, PVD, sputtering, or some other deposition process. Thereafter, a planarization process (e.g., a chemical-mechanical planarization (CMP)) may be performed on the ILD layer to form the first ILD structure 122 a.

Also shown in FIG. 17 , the sacrificial gate 1304 (see, e.g., FIG. 16 ) is removed, thereby forming an opening 1702 that is defined by inner sidewalls of the sidewall spacer 502 and an upper surface of the second conductive structure 116. In some embodiments, a process for removing the sacrificial gate 1304 comprises performing an etch (e.g., dry or wet etch) to selectively remove the sacrificial gate 1304. In further embodiments, before the etch, a masking layer (not shown) may be formed covering the first ILD structure 122 a and the sidewall spacer 502, while leaving the sacrificial gate 1304 exposed. Thereafter, the etch is performed with the masking layer in place, thereby selectively removing the sacrificial gate 1304. Subsequently, the masking layer may be stripped away.

As shown in FIG. 18 , a gate electrode layer 1802 is formed filling the opening 1702 and over the second conductive structure 116, the sidewall spacer 502, and the first ILD structure 122 a. The gate electrode layer 1802 is conductive and may comprise, for example, a metal W, Al, Ti, Mo, or the like. In some embodiments, the gate electrode layer 1802 may be formed by CVD, PVD, ALD, sputtering, electrochemical plating, electroless plating, or some other deposition process.

In some embodiments, before the gate electrode layer 1802 is formed, a capping layer (not shown) may be formed lining the opening 1702 and over the second conductive structure 116, the sidewall spacer 502, and the first ILD structure 122 a. In such embodiments, the gate electrode layer 1802 may be formed on the capping layer. The capping layer may comprise, for example, TiN, TaN, or the like. In further embodiments, the capping layer may be formed by CVD, PVD, ALD, sputtering, or some other deposition process. In yet further embodiments, the gate electrode layer 1802 and/or the capping layer has an overall electronegativity that is less than the overall electronegativity of the ferroelectric structure 114.

As shown in FIG. 19 , a gate electrode 118 is formed on the second conductive structure 116 and between the inner sidewalls of the sidewall spacer 502. In some embodiments, a process for forming the gate electrode 118 comprises performing a planarization process (e.g., CMP) into the gate electrode layer 1802 (see, e.g., FIG. 18 ). The planarization process removes an upper portion of the gate electrode layer 1802, thereby forming the gate electrode 118. In further embodiments, after the gate electrode 118 is formed, formation of a device gate stack 120 is complete, which may also complete formation of a first wakeup-free ferroelectric memory device 101 a. In yet further embodiments, the process of forming the device gate stack 120 as described above may be referred to as a gate-last high-k/metal gate (HKMG) process.

It will be appreciated that, in some embodiments, the device gate stack 120 may be formed by other processes. For example, the device gate stack 120 may be formed by a gate-first HKMG process (e.g., the metal gate electrode is formed prior to source/drain formation), a fully silicided (FUSI) metal gate process (e.g., fully siliciding a polysilicon gate), or a doped polysilicon gate process (e.g., self-aligned polysilicon gate process). Depending on the process in which the device gate stack 120 is formed, the processing layer may comprise, for example, doped polysilicon (e.g., n-type/p-type polysilicon), undoped polysilicon, a metal (e.g., W, Al, Ti, Mo, or the like), a metal-nitride (e.g., TiN, TaN, or the like), some other conductive material, or a combination of the foregoing.

As shown in FIG. 20 , a second ILD structure 122 b, a plurality of conductive contacts 124, a plurality of conductive lines 402, and a plurality of conductive vias 404 are formed over the first ILD structure 122 a and the first wakeup-free ferroelectric memory device 101 a. The second ILD structure 122 b may be formed with a substantially planar upper surface. In some embodiments, a process for forming the second ILD structure 122 b comprises depositing a plurality of ILD layers, which are stacked on one another, over the first ILD structure 122 a and the first wakeup-free ferroelectric memory device 101 a. The ILD layers may be deposited by CVD, PVD, sputtering, or some other deposition process. In further embodiments, a planarization process (e.g., CMP) may be performed on one or more of the plurality of ILD layers.

In some embodiments, a process for forming the plurality of conductive contacts 124 comprises forming a first ILD layer on the first ILD structure 122 a, the sidewall spacer 502, and the gate electrode 118. Thereafter, the first ILD layer and the first ILD structure 122 a are selectively etched to form contact openings (not shown) that correspond to the plurality of conductive contacts 124. A conductive material (e.g., W) is then deposited on the first ILD layer and filling the contacts opening. Subsequently, a planarization process (e.g., CMP) is performed into the conductive material and the first ILD layer, thereby forming the plurality of conductive contacts 124 extending through the first ILD structure 122 a. In further embodiments, the conductive material may be deposited by CVD, PVD, ALD, sputtering, electrochemical plating, electroless plating, or some other deposition process.

In some embodiments, a process for forming the plurality of conductive lines 402 and the plurality of conductive vias 404 comprises forming a second ILD layer over the plurality of conductive contacts 124 and the first ILD layer. The second ILD layer is selectively etched to form a first set of conductive line openings (not shown) that correspond to a first set of conductive lines of the plurality of conductive lines 402. A conductive material (e.g., Cu) is deposited on the second ILD layer and filling the first set of conductive line openings. A planarization process (e.g., CMP) is performed into the conductive material and the second ILD layer, thereby forming the first set of conductive lines.

Thereafter, a third ILD layer is formed over the first set of conductive lines and the second ILD layer. The third ILD layer is selectively etched to form a first set of conductive via openings (not shown) that correspond to a first set of conductive vias of the plurality of conductive vias 404. A conductive material (e.g., Cu) is deposited on the third ILD layer and filling the first set of conductive via openings. A planarization process (e.g., CMP) is performed into the conductive material and the third ILD layer, thereby forming the first set of conductive vias. This process (e.g., alternating formation of conductive lines and vias) is repeated until the plurality of conductive lines 402 and the plurality of conductive vias 404 are formed.

While FIGS. 11-20 illustrate some embodiments for forming the first IC 100 of FIG. 5 , it will be appreciated that, in some embodiments, the second IC 700 of FIG. 10 may be formed by substantially similar processes. For example, the first electrode 902 and the second electrode 904 may be formed by a process(es) substantially similar to the process(es) described above regarding formation of the plurality of conductive contacts 124, the plurality of conductive lines 402, and/or the plurality of conductive vias 404 (see, e.g., FIG. 20 ). Further, the second conductive structure 116, the ferroelectric structure 114, and the first conductive structure 112 of the second IC 700 may be formed by a process(es) substantially similar to the process(es) described above regarding formation of the second conductive structure 116, the ferroelectric structure 114, and/or the first conductive structure 112 (see, e.g., FIGS. 12-13 ). Moreover, the lower ILD structure 704, the middle ILD structure 706, and/or the upper ILD structure 708 may be formed by a process(es) substantially similar to the process(es) described above regarding formation of the first ILD structure 122 a and/or the second ILD structure 122 b (see, e.g., FIG. 17 and FIG. 20 ).

FIG. 21 illustrates a flowchart 2100 of some embodiments of a method for forming an integrated chip (IC) comprising a front-end-of-line wakeup-free ferroelectric memory device. The front-end-of-line wakeup-free ferroelectric memory device may be the first wakeup-free ferroelectric memory device 101 a. While the flowchart 2100 of FIG. 21 is illustrated and described herein as a series of acts or events, it will be appreciated that the illustrated ordering of such acts or events is not to be interpreted in a limiting sense. For example, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein. Further, not all illustrated acts may be required to implement one or more aspects or embodiments of the description herein, and one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases.

At act 2102, an initial gate stack comprising a polarization switching between a sacrificial gate and a gate dielectric is formed over a semiconductor substrate. The polarization switching structure comprises a ferroelectric structure between a first conductive structure and a second conductive structure, where both an overall electronegativity of the first conductive structure and an overall electronegativity of the second conductive structure are greater than or equal to an overall electronegativity of the ferroelectric structure. FIGS. 11-13 illustrate a series of cross-sectional views of some embodiments corresponding to act 2102.

At act 2104, lightly-doped source/drain extensions are formed in the semiconductor substrate and on opposite sides of the initial gate stack. FIG. 14 illustrates a cross-sectional view of some embodiments corresponding to act 2104.

At act 2106, a sidewall spacer is formed over the semiconductor substrate and along sides of the initial gate stack. FIG. 15 illustrates a cross-sectional view of some embodiments corresponding to act 2106.

At act 2108, source/drain regions are formed in the semiconductor substrate and on opposite sides of the sidewall spacer. FIG. 16 illustrates a cross-sectional view of some embodiments corresponding to act 2108.

At act 2110, the sacrificial gate is removed, thereby forming an opening. FIG. 17 illustrates a cross-sectional view of some embodiments corresponding to act 2110.

At act 2112, a gate electrode is formed in the opening, thereby forming a device gate stack. FIGS. 18-19 illustrate a series of cross-sectional views of some embodiments corresponding to act 2112.

At act 2114, an interconnect structure is formed over the semiconductor substrate and the device gate stack. FIG. 20 illustrates a cross-sectional view of some embodiments corresponding to act 2114.

FIG. 22 illustrates a flowchart 2200 of some embodiments of a method for forming an integrated chip (IC) comprising a back-end-of-line wakeup-free ferroelectric memory device. The back-end-of-line wakeup-free ferroelectric memory device may be the second wakeup-free ferroelectric memory device 101b. While the flowchart 2200 of FIG. 22 is illustrated and described herein as a series of acts or events, it will be appreciated that the illustrated ordering of such acts or events is not to be interpreted in a limiting sense. For example, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein. Further, not all illustrated acts may be required to implement one or more aspects or embodiments of the description herein, and one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases.

At act 2202, a front-end-of-line semiconductor device is formed on a semiconductor substrate.

In some embodiments, the front-end-of-line semiconductor device may be, for example, a metal-oxide semiconductor field-effect transistors (MOSFETs), bipolar junction transistors (BJTs), high-electron-mobility transistors (HEMTs), or any other front-end-of-line semiconductor device. In some embodiments, the front-end-of-line semiconductor device may be formed by process(es) substantially similar to process(es) described above regarding formation of the first wakeup-free ferroelectric memory device 101 a (see, e.g., FIGS. 11-19 ). For example, the process(es) to form the isolation structure 104, the gate dielectric 108, the lightly-doped source/drain extensions 504 a-b, the sidewall spacer 502, the source/drain regions 106 a-b, and/or the gate electrode 118.

At act 2204, a first portion of an interconnect structure is formed over the front-end-of-line semiconductor device and the semiconductor substrate, where the first portion of the interconnect structure comprises a first plurality of conductive features disposed in a lower interlayer dielectric (ILD) structure.

In some embodiments, the first plurality of conductive features may be substantially similar to one or more of the plurality of conductive contacts 124, the plurality of conductive lines 402, and/or the plurality of conductive vias 404. In further embodiments, the lower ILD structure may be substantially similar to a portion of the ILD structure 122. In yet further embodiments, the first portion of the interconnect structure may be formed by process(es) substantially similar to process(es) described above regarding formation of the first ILD structure 122 a, the second ILD structure 122 b, the plurality of conductive contacts 124, the plurality of conductive lines 402, and/or the plurality of conductive vias 404 (see, e.g., FIG. 17 and/or FIG. 20 ).

At act 2206, a polarization switching structure comprising a ferroelectric structure between a first conductive structure and a second conductive structure is formed over the first portion of the interconnect structure, where both an overall electronegativity of the first conductive structure and an overall electronegativity of the second conductive structure are greater than or equal to an overall electronegativity of the ferroelectric structure, and where the first portion of the interconnect structure electrically couples the polarization switching structure to the front-end-of-line semiconductor device.

In some embodiments, the polarization switching structure 110 may be formed over the portion of the interconnect structure by process(es) substantially similar to process(es) described above regarding formation of the polarization switching structure 110 of the first wakeup-free ferroelectric memory device 101 a (see, e.g., FIGS. 11-13 ). For example, the process(es) to form the first conductive structure 112, the ferroelectric structure 114, and/or the second conductive structure 116.

At act 2208, a middle ILD structure is formed over the first portion of the interconnect structure and around the polarization switching structure.

In some embodiments, the middle ILD structure may be substantially similar to a portion of the ILD structure 122. In further embodiments, the middle ILD structure may be formed by process(es) substantially similar to process(es) described above regarding formation of the first ILD structure 122 a and/or the second ILD structure 122 b (see, e.g., FIG. 17 and/or FIG. 20 ).

At act 2210, a second portion of the interconnect structure is formed over the middle ILD structure and the polarization switching structure, where the second portion of the interconnect structure comprises a second plurality of conductive features disposed in an upper ILD structure.

In some embodiments, the second plurality of conductive features may be substantially similar to one or more of the plurality of conductive contacts 124, the plurality of conductive lines 402, and/or the plurality of conductive vias 404. In further embodiments, the upper ILD structure may be substantially similar to a portion of the ILD structure 122. In yet further embodiments, the second portion of an interconnect structure may be formed by process(es) substantially similar to process(es) described above regarding formation of the first ILD structure 122 a, the second ILD structure 122 b, the plurality of conductive contacts 124, the plurality of conductive lines 402, and/or the plurality of conductive vias 404 (see, e.g., FIG. 17 and/or FIG. 20 ).

In some embodiments, the present application provides a ferroelectric memory device. The ferroelectric memory device comprises a pair of source/drain regions disposed in a semiconductor substrate. A gate dielectric is disposed over the semiconductor substrate and between the source/drain regions. A first conductive structure is disposed on the gate dielectric. A first ferroelectric structure is disposed on the first conductive structure. A second conductive structure is disposed on the ferroelectric structure, where both the first conductive structure and the second conductive structure have an overall electronegativity that is greater than or equal to an overall electronegativity of the ferroelectric structure.

In some embodiments, the present application provides an integrated chip (IC). The IC comprises a semiconductor device disposed on a semiconductor substrate. A first interlayer dielectric (ILD) structure is disposed over the semiconductor device and the semiconductor substrate. A first conductive via is disposed in the first ILD structure and electrically coupled to the semiconductor device. A polarization switching disposed over the first ILD structure and electrically coupled to the first conductive via, where the polarization switching structure comprises a ferroelectric structure disposed between a first conductive structure and a second conductive structure, and where both the first conductive structure and the second conductive structure have an overall electronegativity that is greater than or equal to an overall electronegativity of the ferroelectric structure

In some embodiments, the present application provides a method for forming a ferroelectric memory device. The method comprises forming a dielectric layer over a semiconductor substrate. A first conductive layer is formed over the dielectric layer, where the first conductive layer has a first overall electronegativity. A ferroelectric layer is formed on the first conductive layer, where the ferroelectric layer has a second overall electronegativity that is less than or equal to the first overall electronegativity. A second conductive layer is formed on the ferroelectric layer, where the second conductive layer has a third overall electronegativity that is greater than or equal to the second electronegativity. The second conductive layer, the ferroelectric layer, and the first conductive layer are etched to from a polarization switching structure over the semiconductor substrate. A first conductive via is formed over the polarization switching structure and electrically coupled to the polarization switching structure.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A method for forming a ferroelectric memory device, comprising: forming a dielectric layer over a semiconductor substrate; forming a first conductive layer over the dielectric layer, wherein the first conductive layer has a first overall electronegativity; forming a ferroelectric layer on the first conductive layer, wherein the ferroelectric layer has a second overall electronegativity that is less than or equal to the first overall electronegativity; forming a second conductive layer on the ferroelectric layer, wherein the second conductive layer has a third overall electronegativity that is greater than or equal to the second overall electronegativity; etching the second conductive layer, the ferroelectric layer, and the first conductive layer to form a polarization switching structure over the semiconductor substrate; depositing an interlayer dielectric (ILD) layer over the polarization switching structure; performing a planarization process on the ILD layer to form an ILD structure surrounding the polarization switching structure; and forming a first conductive via over the polarization switching structure.
 2. The method of claim 1, wherein the first conductive layer, the second conductive layer, and the ferroelectric layer have maximum widths that are substantially equal after being etched.
 3. The method of claim 1, wherein the first conductive layer and the second conductive layer respectively comprise polysilicon having an n-type doping or polysilicon having a p-type doping.
 4. The method of claim 1, wherein the first conductive layer and the second conductive layer respectively comprise iridium.
 5. The method of claim 1, further comprising: forming a sacrificial layer over the second conductive layer prior to depositing the ILD layer; and removing the sacrificial layer from over the polarization switching structure after performing the planarization process and before forming the first conductive via.
 6. The method of claim 1, further comprising: forming one or more dielectric spacers along opposing sides of the polarization switching structure; and forming the ILD layer along one or more sidewalls of the one or more dielectric spacers.
 7. The method of claim 6, wherein the one or more dielectric spacers continuously extend from vertically below a bottom of the polarization switching structure to vertically above a top of the polarization switching structure.
 8. The method of claim 1, further comprising: forming a semiconductor device on the semiconductor substrate, wherein the semiconductor device comprises a gate electrode disposed over the semiconductor substrate; and wherein a first conductive via is configured to electrically couple the gate electrode of the semiconductor device to the polarization switching structure.
 9. A method for forming a ferroelectric memory device, comprising: forming a dielectric layer over a substrate; forming a ferroelectric device stack over the dielectric layer, the ferroelectric device stack comprising a first conductive layer over the dielectric layer, a ferroelectric layer on the first conductive layer, and a second conductive layer on the ferroelectric layer, wherein the ferroelectric layer has a smaller electronegativity than the first conductive layer and the second conductive layer; forming a processing layer over the second conductive layer; etching the ferroelectric device stack and the processing layer to form a polarization switching structure covered by a sacrificial gate; forming an interlayer dielectric (ILD) structure on opposing sides of the polarization switching structure and the sacrificial gate; removing the sacrificial gate after forming the ILD structure to form a gate recess; and forming a gate electrode within the gate recess.
 10. The method of claim 9, further comprising: forming one or more sidewall spacers along the opposing sides of the polarization switching structure and the sacrificial gate prior to forming the ILD structure, wherein the one or more sidewall spacers laterally separate the polarization switching structure and the sacrificial gate from the ILD structure.
 11. The method of claim 10, wherein a bottom surface of the gate electrode is disposed vertically between the substrate and an upper surface of the one or more sidewall spacers.
 12. The method of claim 9, wherein the second conductive layer and the gate electrode have maximum widths that are substantially equal.
 13. The method of claim 9, wherein the polarization switching structure has a surface area that is between approximately 1 square nanometer and approximately 100 square micrometers.
 14. The method of claim 9, wherein the second conductive layer is completely confined above a top surface of the ferroelectric layer after etching the ferroelectric device stack.
 15. A method for forming a ferroelectric memory device, comprising: forming a dielectric over a substrate; forming a ferroelectric device stack over the dielectric; etching the ferroelectric device stack to form a polarization switching structure over the dielectric, the polarization switching structure comprising a ferroelectric structure disposed between a first conductive structure and a second conductive structure, wherein the ferroelectric structure has a smaller electronegativity than the first conductive structure and the second conductive structure; and wherein opposite outermost sidewalls of the first conductive structure, the ferroelectric structure, and the second conductive structure are separated by distances that are substantially the same.
 16. The method of claim 15, further comprising: forming a semiconductor device on the substrate, wherein the semiconductor device comprises a gate electrode disposed over the substrate; and forming a conductive interconnect over the substrate, the conductive interconnect configured to electrically couple the gate electrode of the semiconductor device to the polarization switching structure.
 17. The method of claim 15, wherein the first conductive structure and the second conductive structure respectively comprise doped polysilicon.
 18. The method of claim 15, further comprising: forming a first electrode to contact an upper surface of a first conductive via over the substrate; forming the first conductive structure to contact an upper surface of the first electrode, wherein an overall electronegativity of the first conductive structure is greater than or equal to an overall electronegativity of the first electrode; forming a second electrode to contact an upper surface of the second conductive structure; and forming a second conductive via to contact an upper surface of the second electrode, wherein an overall electronegativity of the second conductive structure is greater than or equal to an overall electronegativity of the second electrode.
 19. The method of claim 18, wherein an overall electronegativity of the first conductive via is less than or equal to the overall electronegativity of the second conductive structure.
 20. The method of claim 15, wherein the first conductive structure has a first thickness that is in a first range of between approximately 0.1 nanometer and approximately 1,000 nanometers; and wherein the ferroelectric structure has a second thickness that is in a second range of between approximately 1 nanometer and approximately 100 nanometers. 